Connection of a catheter to a blood vessel, for example a vein, is an important medical procedure that allows withdrawal of fluid, for example blood samples, or delivery of fluid, for example nutrients, for a few days up to a few weeks. In the process of fluid delivery and/or withdrawal, for example, the catheter is periodically pulled out of one vein area and inserted into another vein area, for example, every five days.
FIGS. 1A through 1F illustrate typical prior art catheters and a variety of problems that typically occur, resulting in obstruction of fluid withdrawal, for example, from a vein 130.
FIG. 1A illustrates a catheter 118, typically comprising a hollow tube, a portion of which is typically implanted vein 130 by piercing a section of skin 102 and wall of vein 130. By so doing, a catheter front inlet 134 lies within vein 130.
Vein 130 is most desirable when it is located just below skin 102 so that the outline of vein 130 can be seen through skin 102. This allows a relatively painless and fast percutaneous maneuver to poke catheter 118 into vein 130. In FIG. 1F, prior art catheter 118 is shown installed percutaneously in an arm 104 into vein 130 whose outline is seen through skin 102. For the purpose of delivery of nutrients to vein 130, catheter 118, for example, is attached to a flexible sac 106 containing a fluid 108. Sac 106 is, for example, held by a hook 112 that is connected to a stand 110. Fluid 108 is distributed, for example, by gravity action through catheter 118 to vein 130. Additionally or alternatively, fluid 108 is distributed with pressure, for example by a perfusion system that increases the rate of fluid movement for the purpose of decreasing the introduction span of fluid 108.
In prior art catheters, FIGS. 1A-1F, fluids are typically transported from vein 130 through catheter front inlet 134. For example, multiple fluid samples are withdrawn from the patient through catheter front inlet 134 in vein 130. During fluid withdrawal for a moderate period of time, leaving catheter 118 in one place, such as vein 130, for as long as possible, for example several weeks, is advantageous.
Unfortunately, when catheter 118 is left in one place for a few days or even as briefly as one day, particularly when fluid withdrawal is not on a continuous basis, blockage of catheter front inlet 134 often occurs. While blockage may occur either during fluid introduction or withdrawal from a patient, it often occurs in a shorter span of time during fluid withdrawal as blockages are pulled toward front inlet 134. During fluid introduction, for example, blockages tend to be displaced and/or removed away from catheter inlet 134 by the pressure of the movement of fluid out of catheter 118 into vein 130. FIGS. 1A-1E illustrate the various blockages that occur, often more readily, during fluid withdrawal from vein 130.
FIG. 1B illustrates one form of blockage when the surrounding cavity walls 150 collapse, blocking catheter front inlet 134. FIG. 1C demonstrates another form of blockage where a clot 160, consisting of solid particles from body fluid, forms and blocks catheter front inlet 134. Clot 160, for example, may form either beyond front catheter inlet 134, as shown, or within catheter 118, in either case preventing fluid withdrawal. In some cases, clot 160 forms as a plug both inside and outside of inlet 134. FIG. 1D demonstrates another form of blockage where a section of inflamed tissue 170 blocks front inlet 134. FIG. 1E illustrates still another form of blockage that occurs when vein valves 194, a regularly occurring part of the body's vein system, block inlet 134.
In all of these cases, vein 130 becomes unsuitable, often permanently, for further fluid withdrawal. When vein 130 becomes unsuitable, catheter 118 must be taken out of vein 130 and inserted into another vein 130. Unfortunately, besides the discomfort associated with reinsertion of catheter 118 into vein 130, there is a limit to the number of fluid exchange areas, such as vein 130, that, for example, may be percutaneously accessed with catheter 118.
When easily accessed venous fluid withdrawal areas are exhausted, less optimal areas must be utilized, such as, for example, veins that are somewhat tortuous, often requiring more than one attempt for a successful introduction of catheter 118 into vein 130. Eventually, when percutaneously accessible fluid exchange areas are exhausted, fluid withdrawal and/or introduction, for example, can take place only through alternative means such as a surgically placed shunt. The placement of a shunt is a relatively expensive and hazardous procedure in comparison to percutaneous access of vein 130 with catheter 118.
Zumschlinge, U.S. Pat. No. 6,077,248 teaches a catheter that is used for fluid withdrawal from body cavities with a needle that retracts into a flexible housing to prevent the needle from causing tissue damage due to tissue movement against the needle.